Have you ever seen a lighthouse? If you live along a major coastline or have traveled near water, there’s a good chance that you have. You might have spotted a lighthouse while walking along a beach, fishing, or sailing. Perhaps you have visited a museum about lighthouses or climbed to the top of an old lighthouse tower. Even if you have never seen a lighthouse up close, you have a good idea what one looks like. Pictures of lighthouses adorn the covers of books, magazines, greeting cards—even the bags of one brand of potato chips. Lighthouses flash at us from movies and TV ads.

Long before lighthouses were part of summer vacations or company advertising, they were essential parts of the landscape. At a time when rivers and oceans were the nation’s highways, lighthouses served as warning signs, traffic lights, and maps, all rolled into one. Without lighthouses, it was harder for ships to get from one port to another safely. Without ships, it was difficult or impossible to send goods from one part of the country to another or obtain them from other nations. Without trade, people could not earn a living. In fact, the very growth and survival of the United States depended on a large network of reliable lighthouses.